Asphalt is used in a variety of applications, but by far the major use is in road construction and maintenance. Although it is a versatile material, the physical properties of asphalt may limit its usefulness in this and other applications. For quite a number of years researchers have demonstrated that the addition of certain polymersxcx9c3 to about 8 wt. % or more can enhance the properties of asphalt. These include:
Increased toughness and tenacity
Increased tack, elasticity and improved impact resistance
Resistance to deformation at low temperatures, and
Resistance to deformation at high temperatures.
While a number of thermoplastics can confer the above properties to asphalt to a surprisingly high degree, there remains a serious problem, which the polymer generally does not address. This involves the interfacial surface energy between the aggregate, about 95 wt. %, and the bitumen, about 5 wt. %. Usually, a polymer is added to the above asphalt composite from about 5 to 25 wt. % based on the bitumen. The aggregate is highly hydrophilic while most polymers tend to be very hydrophobic. The result is delamination of the materials, particularly during freeze-thaw cycles, high temperatures and the exposure to salt, oil, gasoline, water etc.
This invention will describe methods of circumventing this very serious problem. The methods will be economically viable based on the utility of inexpensive raw materials and high production rate processes. The disclosure is also versatile in that it can be used with most of the current polyolefins presently being used to modify asphalt.
Other benefits are also inherent with this invention, such as the ease of dispersing the polymers with the asphalt. This is a particularly difficult and costly problem for polyolefins, most times requiring special high energy mixing equipment. The added expense can negate using this technology due to budgetary problems confronted by many states.
At low temperatures asphalt can turn brittle and crack: at high temperatures, it can soften when under the weight of heavy trucks passing over it. A road may be 80-100xc2x0 F. hotter than it is in winter; and for every 100xc2x0 F. rise in temperature, asphalt is a million times softer. Though it never actually runs off the road, it does creep into ridges and ruts that make driving dangerous. An asphalt road would hold up better with more built-in sturdiness.
Polymers work by creating a kind of support matrix within the asphalt. A seminal paper by JEW et al (J. Appl. Polym. Sci, 31,2685-2704 (1986)) confirmed that 8 wt. % polyethylene in a bitumen mixture possessed:
Increased flexural strength
Increased flexural modulus
Increased elongation
Increased fracture energy
These investigators concluded that a polyethylene in hot-mix paving materials can extend service temperature range at both high and low temperatures, thereby simultaneously reducing both pavement distortion (rutting) and low temperature cracking so that pavement lifetimes can be more than doubled.
These investigators also suggest the use of Kraton G (tri-block polymer) to control the stability of the mixture, particle size and compatibility of the dispersed polyethylene phase. However, this approach is not economically feasible due to the high weight percent of the polymers used and the costs for processing the asphalt-polymer blend.
The invention relates to polymers, which have been functionalized so as to contain one or more functional groups selected from the group consisting of amino, imino, imido and imidazloyl groups as well as processes for preparing such functionalized polymers. The functionalized polymer, when mixed with bitumen and aggregate provides for an excellent paving composition with improved physical properties and enhanced anti-stripping properties.
Many commodity polymers upon modification using the technology of this invention can be utilized. These include plastomers and elastomers whose compositions consist of polyolefins, styrene-alpha olefins, and polydienes.
Specifically, modified polyethylene, polypropylene, polyethylene-polypropylene copolymers or terpolymers, styrene-ethylene interpolymers, chlorosulfonated polyethylene, or polyisoprene. These are the preferred modified polymers.
This invention teaches the reaction of polyamines or polyether amines with the before described preferred polymers as being high desired polymer asphalt modifiers. There are basically two chemical reactions in which this invention modifies the desired polymers with polyamines. These are classified as amidation and amination.
Amidation involves the reaction of a carboxylic acid or an anhydridexe2x80x94with a polyamine, while amination involves either a grafting of a polyamine to the polymer backbone or by reacting a polyamine with a carbonyl functionality in the polymer or with a tertiary or secondary carbon atom in the polymer macromolecule. U.S. Pat. Nos. 4,068,056; 4,068,057; and 4,068,058 describe amination of polyolefins.
This invention also teaches methods in preparing the modified polymers, and subsequent blending with the asphalt. The compositions of value as polymer asphalt modifiers can be prepared by chemical solution reactions, intensive mixing devices, or in-situ in the presence of hot asphalt. Obviously, where appropriate the in-situ process offers considerable costs advantage over the other methods. Nevertheless, extrusion, single or twin screw, is also an economical viable process. Chemical solution modified is not preferred due to the considerable costs associated with this procedure.
The first embodiment of the invention relates to polymers, which have been functionalized so as to contain one or more functional groups selected from the group consisting of amino, amido, imino, imido and imidazloyl groups as well as processes for preparing such functionalized polymers. Typically, the polymer prior to functionalization will have a number average molecular weight of 5,000 to about 500,000.
Subsequent to functionalization, the functionalized polymer will have a nitrogen content of about 0.05 to about 4.50 wt. %, based on the weight of the functionalized polymer. Suitable polymers for functionalization include polyolefins, elastomers, thermoplastic elastomers, and styrene-alpha olefin interpolymers.
Typically, the polyolefin will be a homopolymer of a C2-C8 olefin, a copolymer of two or more C2-C8 olefins; a copolymer of one or more C2-C8 olefins and a polymerizable monomer or a graft copolymer of one or more C2-C8 olefins and a polymerizable monomer. Suitable C2-C8 olefins include ethylene; propylene; a mixture of ethylene and propylene; butylenes; isoprene; and butadiene. Preferably the homopolymer is a polyethylene or a polypropylene. Suitable polyethylenes include low-density polyethylene, high-density polyethylene, linear low-density polyethylene, linear high-density polyethylene and metallocene polyethylene. Suitable polypropylenes include isotactic, syndiotactic and/or atactic polypropylene.
Preferably, the copolymer of two or more C2-C8 olefins comprises an amorphous or elastomeric copolymer of ethylene and propylene wherein the molar ratio of ethylene to propylene is the range of about 0.2:1 to about 3:1.
In the case of the polymer being a copolymer of one or more C2-C8 olefins and a polymerizable monomer, a suitable copolymer comprises an ethylene-propylene-diene monomer terpolymer, wherein the diene monomer is selected from the group consisting of 1,4-hexadiene; dicyclopentadiene; and ethylidene norbomene.
Suitably, the polymerizable monomer is selected from the group consisting of styrene C3-C15 (meth) acrylates, vinyl acetates, vinyl carboxylic acids and vinyl carboxylic acid anhydrides. Preferably, the C2-C8 olefins are selected from the group consisting of ethylene, propylene, a mixture of ethylene and propylene, and butylenes, and the polymerizable monomer comprising styrene.
In the case of the polymer being a graft polymer, suitable graft polymers include polyethylene and maleic anhydride, polypropylene and maleic anhydride and an ethylene-propylene copolymer and maleic anhydride.
In the case of the polymer being a copolymer of two or more C2-C8 olefins suitable copolymers are those of ethylene or propylene and an alpha-olefin selected from the group consisting of 1-butene, 1-hexene, 1-octene and vinyl cyclohexane.
In the case of the polymer being an elastomer, the elastomer may be virgin or reclaimed crumb rubber. In the case of the polymer being a thermoplastic elastomer, suitable thermoplastic elastomers include a styrene-xcex1-olefin block copolymer, a blend of polypropylene and ethylene propylene rubber, a blend of polypropylene and ethylene propylene diene monomer, a blend of polypropylene and a poly(xcex1-olefin), a multi-block copolymer of polyethylene and a poly(xcex1-olefin), a multi-block copolymer of polypropylene and a poly(xcex1-olefin); and mixtures thereof.
Other commercial elastomeric polymers, which can be modified with the polyamines of this invention, are chlorosulfonated polyethylene and polyisoprene. Both the chloro and sulfonyl chloride functions will react with the polyamines to give a useful polymer asphalt modifier having improved physical and chemical properties.
The functionalized polymer is readily prepared by reacting the desired polymer with a polyamine or polyamine ether in the presence of an oxygen-containing gas, e.g., air, and/or a peroxide and/or a diazo initiator. Typically, the reaction is carried out at a temperature of about 140 to about 280 C, preferably in two steps: (a) oxidizing the polymer with the oxygen-containing gas and/or peroxide and/or diazo initiator; and (b) reacting the oxidized polymer resulting from step (1) with an amine or amine ether to produce the functionalized polymer. Typically, after oxidation, the oxidized polymer will have functionalities capable of reacting with amines, amine-ethers, and/or hydroxy amines.
Preferably the reaction is carried out by mixing the oxidized polymer and the amine or amine ether at an agitation rate of about 30 to about 150 rpm over a period of time of about 1 to about 4 hours. The mixing is desirably carried out using a device such as Braebender or Banbury mixer, a reactive extruder; and a Farrel continuous mixer. The reaction may be carried out in the absence of any diluent or in the presence of a diluent such as an aromatic hydrocarbon, a paraffinic hydrocarbon, a naphthenic hydrocarbon, asphalt or mixtures thereof.
Suitable peroxides include dicumyl peroxide, di-t-amyl peroxide, diisobutyral peroxide, diisopropyl peroxydicarbonate, t-amyl peroxypivalate, t-butyl peroxypivalate, t-amyl peroxy-2-ethyl-hexanate, t-butyl peroxy-2-ethyl-hexanate, t-butyl peroxyisobutyrate, t-butyl peroxyacetate and t-butyl peroxybenzoate. Suitable diazo initiators include 2,2xe2x80x2-azobis(2,4-dimethylvaleronitrile); 2,2xe2x80x2-azo(2-methylpropane)(2,4-di-methyl-4-methoxy-valeronitrile); 2,2xe2x80x2-azobis(isobutyronitrile); 2,2xe2x80x2-azo(2-methylpropane) (2,4-dimethylvaleronitrile); 2,2xe2x80x2-azo(2-methylbutyronitrile); 2,1-azo(2-methyl-propane) (1-cyano-cyclohexane) and 2,1-azo(2-methylbutane)(1-cyanocyclohexane).
In the case where the desired polymers of this invention have grafted or copolymerized maleic anhydride or acrylic acid, from about 0.05 to about 5.0 wt. %, the reaction with the polyamine or polyamine ether is straight forward resulting in either an imide, amide or imidazole linkage between the polymer and the polyamine.
It has been experimentally determined that this reaction is quite facile in either a high intensity mixer or an extruder.
As mentioned above, the reaction takes place in the presence of an amine or amine ether. Desirably, the amine will contain at least two primary amine groups, at least one secondary amine group and/or at least one primary amine group and one secondary amine group, e.g., a polyalkyleneamine containing primary, secondary and/or tertiary monoamine and/or diamines groups containing a total of about 2 to about 60 carbon atoms. Preferably, the polyalkyleneamine contains repeating alkylene groups containing about 2 to about 12 carbon atoms. Preferably, the polyalkyleneamine comprises a polyethyleneamine, e.g., diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and higher homologs thereof, and mixtures of the foregoing polyethyleneamines having an average molecular weight of about 100 to about 4,000. Alternatively, the polyalkyleneamine may preferably be a polypropyleneamine, especially a polypropyleneamine having the general formula: R2N[(CH2)3N]n(CH2)3NR2, wherein n is an integer having a value of 1 to 6 and R is hydrogen or methyl. Particularly preferred is a heavy polyamine comprising a complex mixture of linear, branched and cyclic polyethyleneamines wherein the structures of the principal components of the heavy polyamine contain 6 or more nitrogen atoms per molecule.
Typically, the amine ether will be a polyoxyalkyleneamine containing primary monoamine, diamine and/or triamine groups attached to the terminus of a polyether backbone and will have a number average molecular weight of about 89 to about 5,000. Preferably, the polyether backbone is based on propylene oxide, ethylene oxide or mixed propylene oxide/ethylene oxide, e.g., a polyether primary amine which is derived from a nonylphenolethoxylate and has an ethylene oxide number of about 1 to about 10 and an amine value of about 1.3 to about 2.6 meq/g.
The functionalized polymers of the invention are useful for admixture with asphalt and preferably also with one or more fillers. The resultant admixture is particularly useful for applications such as paving compositions as well as for roofing compositions. As is well known, asphalt is a naturally occurring or pyrolytically obtained substance of dark color consisting almost entirely of carbon and hydrogen, with very little oxygen, nitrogen or sulfur. Asphalt generally understood to embrace the materials commonly known as coal tar, pitch or bitumen, including petroleum derived bitumen and naturally occurring bitumen such as lake asphalt and Gilsonite.
Typically, the functionalized polymer is present in the admixture with the bitumen in the amount of about 0.5 to 5.0 wt. %, based on the weight of the mixture. Preferably, the mixture also will contain from about 70 to about 95 wt. % of a filler, based on the total weight of asphalt functionalized polymer; and filler. Suitable fillers include aggregate; inorganic fibers; organic fibers; clays; minerals; sand; and mixtures thereof. The mixture may also contain an extender oil, preferably in the amount of about 1 to about 40 wt. %, based on the weight of the asphalt. Typically, the asphalt functionalized polymer and filler are mixed together at a temperature of about 80 to about 200 C. The functionalized polymer may be mixed with the asphalt and optionally with a filler or the polymer may be functionalized, i.e. oxidize and reacted with the amine or amine ether in the presence of the asphalt and optionally in the presence of a filler.
A further embodiment of the invention relates to a thermoplastic elastomer comprising a modified copolymer of a styrene monomer and a polymerizable comonomer. Suitable styrene monomers include styrene, methylstyrene and isopropyl styrene. Suitable polymerizable comonomers include one or more C4-C12 dienes, one or more C2-C8 olefins, one or more C3-C15 (meth)acrylates, one or more vinyl carboxylic acids, one or more vinyl carboxylic acid anhydrides and mixtures thereof. Suitable dienes include butadiene, isoprene, chloroprene, 1-4-hexadiene, dicyclopentadiene and ethylidene norbomene. Preferable copolymers are styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers and styrene-ethylene-butadiene-styrene copolymers and the like.
The process for preparing the modified thermoplastic elastomers of the invention involves reacting a copolymer of a styrene monomer and a polymerizable comonomer with an amine or amine ether in the presence of a free radical agent, e.g., a peroxide or a diazo initiator. Suitable peroxides, include dicumyl peroxide, di-t-amyl peroxide, diisobutyral peroxide, diisopropyl peroxydicarbonate, t-amyl peroxypivalate, t-butyl peroxypivalate, t-amyl peroxy-2-ethyl-hexanate, t-butyl peroxy-2-ethyl-hexanate, t-butyl peroxyisobutyrate, t-butyl peroxyacetate and t-butyl peroxybenzoate. Suitable diazo initiators include 2-2xe2x80x2-azobis(2,4-dimethylvaleronitrile); 2,2xe2x80x2-azo(2-methylpropane)2,4-di-emthyl-4-methoxy-valeronitrile); 2,2xe2x80x2-azobis(isobutyronitrile); 2,2xe2x80x2-azo(2-propane) (1-cyano-cyclohexane); and 2,1-azo(2-methylbutane)(1-cyanocyclohexane).
Typically, the reaction of the copolymer of a styrene monomer and a polymerizable comonomer with the amine or amine ether in the presence of the free radical agent is carried out at a temperature of about 140 to about 280 C. Preferably, the copolymer is reacted with an excess of the amine or amine ether such that the resultant aminated copolymer will have a nitrogen content of about 0.1 to about 5 wt. %, based on the weight of the modified copolymer. The amine or amine ether which is reacted with the copolymer may be an of those described above in respect to the preparation of the functionalized polymers of the invention.
Experimental
Polymers
The following polymers (not all inclusive) are suitable for amidation and/or amination according to the teachings of this invention. Preferably the polymers will be most efficacious as a polymer asphalt modifiers if they have a number average molecular weight of about 5,000 to about 500,000. These include any polyethylene, polypropylene, copolymer of ethylene and propylene (EP), EPDM (ethylene propylene diene monomers) or EPR (ethylene propylene rubber) that can be amidated and aminated.
Other preferred polymers include grafted or copolymerized polyethylene, polypropylene, EP, EPDM, EPR with maleic anhydride or acrylic acid followed by amidation. The amount of grafted or copolymerized maleic anhydride or acrylic acid should be from about 0.05 to about 8.0 wt. %.
Other preferred polymers, which can be modified according to this invention, are styrene-xcex1-olefins where the olefin is most preferable ethylene.
Other polymers, which can be modified by polyamines or polyetheramines, are chlorosulfonated polyethylene (CSM) and polychloroprene. These polymers have reactive chlorine atoms, which can undergo nucleophilic substitution with amines in general.
Regarding all of the above described polymers, there should be incorporated from about 0.05 to about 4.50 wt. % nitrogen whose source is a polyamine or polyether amine.
The following list identifies commercial examples of polymers, which have worked using the teachings of our invention by reacting them with amines and/or ether amines.
1. Royal Tuf 490 (Uniroyal)
EPDM grafted with about/wt. % maleic anhydride
2. Kraton FG 1901Xxe2x80x94Shell
SEBS grafted with maleic anhydride
3. Allied Signal Co.
AC-307
Oxidized polyethylenexe2x80x94oxidation number is 7 mg KOH/1 g polymer
4. Nucrel 0411HSxe2x80x94DuPont
Polyethylene-c-methacrylic acid 11.0% methacrylic acid
5. Aldrich Chemicals
Polyethylene grafted with about 0.85 weight percent maleic anhydride
6. Ricon Resins, Inc.
Polybutadiene grafted with maleic anhydride
7. Polybendxe2x80x94Borealis
Polypropylene grafted with maleic anhydride
8. Dow Plastics
Blends of ethylene/styrene Interpolymer
9. Dylark 132xe2x80x94Arco Chemical Co.
Polystyrenexe2x80x94maleic anhydride copolymer containing 6 wt. % anhydride
10. Hypalon 40 DuPont
Chlorosulfonated Polyethylene
11. Exxelor VA 1801xe2x80x94EXXON Chemicals maleic anhydride functionalized elastomeric ethylene copolymer
Polyamines and Polyether Amines
Specific polyamines include (not all inclusive) include the following examples:
1. Heavy polyaminexe2x80x94Union Carbidexe2x80x94A mixture of linear, branched, and cyclic ethyleneamines with the principal components containing six or more nitrogen atoms per molecule. Similar products are available from Dow Chemical, Akzo Nobel and Tosoh Corporation.
2. Bis-aminoethylpiperazinexe2x80x94Union Carbide
3. Amino (bis-aminohexyl)xe2x80x94DuPont
4. Aminoethylethanolaminexe2x80x94Union Carbide
5. Tetraethylenepentaminexe2x80x94Akzo Nobel
6. Triethylenetetraminexe2x80x94Tosoh Corporation
7. SC-62Jxe2x80x94Morton Chemicalxe2x80x94An ethoxylated polyethyleneamine
8. Polyethyleneaminexe2x80x94BASF
9. Jeffamine M-715xe2x80x94Huntsman Chemical Co.
An ethylenexe2x80x94propylene oxide with a terminal amine group
10. Jeffamine D-2000xe2x80x94Huntsman Chemical Co.
A diamine terminated polypropylene glycol
11. Jeffamine ED-900-Huntsman Chemical Co.
A polyether diamine based on predominately polyethylene oxide backbone.
12. Jeffamine EDR-192-Huntsman Chemical Co.
This is trioxyethylenediamine
13. Jeffamine T-3000-Huntsman Chemical Co.
This is the reaction of triols initiator reacted with propylene oxide, followed by amination of the terminal hydroxy group.
Processes to Prepare the Polymer Modified Asphalt of this Invention
There are three methods to prepare the compositions of this invention for use as polymer modified asphalt applications. The various amination and/or amidation reactions can be carried out by solution, intensive mixing and in-situ engineering processes.
Solution
Both amination and amidation can be carried out in high boiling solvents. The solvents used should not contain any reactive hydrogen atoms, which can be abstracted during the course of the chemical reaction. Hydrogen abstraction has the following descending order:
Phenolic greater than benzylic greater than allylic greater than tertiary hydrogen greater than secondary hydrogen greater than primary hydrogen.
It has been our experience that in order to perform the necessary chemical conversions in any process that tertiary hydrogens need to be present in the polymers to undergo amination and/or amidation. Of course, hydrogen abstractions having lower bond energy would be operable as well.
Therefore, in any given solution process to prepare the modified polymers of this invention it would be a prerequisite that the high boiling greater than 150 C, preferably higher, solvent have only secondary or primary hydrogens e.g., mineral oil long chain hydrocarbons.
Intensive Mixing Devices
There are a number of intensive mixing devices which are commercially available. These type mixers can be either batch or continuous.
Internal batch mixers have been widely used in the production of polymer film, sheeting, dispersion and fluxing.
Essentially, internal mixers consist of cylindrical chambers of shells within which materials to be mixed are deformed by rotating blades or rotors. Frequently the blade is divided into two helices of opposite direction of pitch in order to further the shuffling of components within the mixture. Two specific types of intensive mixer are the well-known Banbury, Haake-Buchler Rheomix 600 and Braeblender types.
Continuous mixers (extruders) have many advantages for the purpose of carrying out the polymer modifications of this invention. The rates of production are many fold higher than a batch mixer. Rates as high as over 1,000 kg/hours are possible. Furthermore, no solvents are needed, or at least a bare minimum for dissolving the catalyst is needed.
Either a single or double screw extruder is an ideal mixer to practice this invention. The raw material is automatically fed from feed-hoppers into the first section of the rotor, which acts as a screw conveyor, propelling the material to the mixing section where it undergoes intensive shear between the rotors and the chamber wall, kneading between the rotors, and a rolling action.
Typical (not all-inclusive) extruders that are useful for this invention are made by Werner and Pfferderer (ZSK-30), and Berstorff (ECS-2E25). These are co rotating intermeshing twin-screw extruders. The screws of the extruder are assembled from individual screw elements. The different sections convey, melt, mix and knead.
When using continuous extruders the amidation process can be carried out sequentially which entails first an oxidation step, as previously described, followed by amidation if the oxidized group is a carboxylic acid. If the oxidation step forms a carbonyl group, then amination will occur. If the oxidation step forms a radical (lose of hydrogen atom leaving a radical carbon atom) then amination by the polyamine will be favored. Undoubtedly, in many cases we have investigated both amidation and amination occur in a competitive way depending on the particular polymer, polyamine, oxidant, temperature, time of reaction and other experimental factors.
In-Situ In Presence of Hot Asphalt
We have found that similar improvements in the physical and chemical properties of various asphalts can be accomplished by what we call the xe2x80x9cin-situxe2x80x9d process. By adding the appropriate amount of polyamine and corresponding polymer to hot asphalt the resulting polymer modified asphalt has virtually the same properties as if the polymer additive was prepared first then added to hot asphalt.
The asphalt must be hot and fairly fluid with a temperature between 125 C to about 250 C. The reaction time various from about 1 hour to about 8 hours.
While it is true that asphalt contains functional acid and base sites, these are so minute that they do not deplete the effective concentrations of the polyamine and/or oxidized polymers. The overall effect is that a similar polymer modifier asphalt is formed when utilizing the xe2x80x9cin-situxe2x80x9d process.
Advantages
The advantages of using the polymer-modified asphalt of this invention are the following:
Easily blended into asphalt
Low effective concentrations from about 1.5 to about 3.0 wt. %
Blended viscosity is only very slightly increased
Superior compatibility and storage stability
Superior aging whereby there is little change in viscosity over time
Increases the high temperature SHRP grade at concentrations between 1.5 to about 3.0 wt. %.
Our polymer modified additive can eliminate the use of an anti-stripping agent
Raw material and processing costs are minimized